Tank support



March 1943' E. w. PITTMAN 2,315,453

TANK SUPPORT Filed Aug. 1, 1938 2 Sheets-Sheet 1 J 1 wen H011 E RN E51W. PITTMAN March 30, 1943.

E. w. PITTMAN 2,3155453 TANK SUPPORT 2 Sheets-Sheet 2 Filed Aug. 1, 19381 wen for,

ERNESTW PiTTMAN.

"JMDI 6 MM}? Patented Mar. 30, 1943 UNITED STATES PATENT OFFICE TANKSUPPORT Ernest W. Pittman, Beaumont, Tex., assignor to The PetroleumIron Works Company of Texas Application August I, 1938, Serial No.222,463 2 Claims. (Cl. 220-18) My invention relates to means and methodsof supporting tanks of the type which have curved bottoms. Tanks of thetype which have curved bottoms are usually supported by a plurality ofupright structural members or by supporting walls. With supports of thistype the load is concentrated on the uprights or the walls and it isnecessary to provide a substantial foundation for each upright or wall.The usual practice is to make excavations and to build concrete footingsfor the support of these uprights or walls, and then to build the tankthereon.

The present invention contemplates a support construction for curvedbottom tanks wherein the supporting base may be positioned directly uponearth or can be placed upon any other type of footing so that the loadwill be distributed over the entire horizontal cross sectional area ofthe tank. This invention is particularly advantageous for supportingtanks containing petroleum liquids or other liquids with a superimposedgas or vapor pressure.

It is one of the objects of the invention to provide a tank supportwherein a uniform pressure is applied on the bottom of the tank in orderto support the load therein.

Another object of the invention is to provide a container for a body ofliquid which liquid will serve to support the bottom of the tankstructure.

Still another object of the invention is to support a tank structureupon a body of liquid so as partially to balance the load on the insideand the outside of the tank bottom.

It is also an object of the invention to provide a tank bottom uponwhich the internal and external pressures are partially balanced so thatthe tank bottom need not be constructed of material capable ofsupporting the liquid load in the tank.

- Still another object of the invention is to support a tank upon a bodyof liquid and to provide gauges to indicate the internal and externalpressures.

A still further object is to provide, in combination with a liquidsupported tank, an arrangement for a stand pipe so that the pressure ofthe liquid supporting the tank can be varied in accordance with thetotal weight of the tank and contents thereof so as to balance theinternal and external pressures on the base of the closed compartment,

Other and further objects of the invention readily will be apparent whenthe following description is considered in connection with theaccompanying drawings wherein:

Fig. 1 shows a vertical sectional View of the tank and its support andillustrates the arrangement of the parts.

Fig. 2 shows a similar view of a spherical tank.

It is a well known principle of hydraulics that the fluid pressurewithin any region of a closed container at the bottom of a stand pipe isa function of the density of the fluid and the head, regardless of theextent of the closed container and of the cross sectional area of thestand pipe, neglecting fluid friction and capillarity. Primarily, myinvention is an adaptation of this principle to the hydraulic support oflarge tanks. The liquid content of the tank is supported by the fluidWithin the closed container, and the entire weight of liquid content oftank and fluid within the closed container and stand pipe thence isdistributed directly to the supporting foundation with uniform unitpressure over the entire cross sectional area of the bottom.

The earth formation upon which the tank is to be deposited isillustrated generally at 2 and of course may be of any desired locationwhere the tank is to be erected. This earth formation may be leveled ofiand the support construction 3 applied directly upon the earths surface,or if desired a thin slab of concrete or other supporting material 4 maybe deposited on the earth in a slight excavation 5. The provision ofsuch a material would merely insure a uniform compactness of the surfaceon which the tank is to be erected.

The tank support generally includes the base I. which may be a fiatplate assembly by welding or otherwise which is of an area approximatelyequal to the horizontal cross sectional area of the tank.

Around the edge of this base 1 is an upright wall 8 which may be of anydesired height depending upon the curvature of the tank bottom ll whichis to be disposed therein. The bottom 9 may take any desiredconfiguration depending upon the tank being constructed but it isintended that the side walls 8 and the curved surface 9 will mergetogether as at In and be suit ably welded or otherwise fixed together soas to form a fluid tight joint at the elevation 10 entirelyaround thetank. In this manner a closed chamber 12 is provided which is defined bythe base I, the side walls 8 and the bottom 9. This chamber I2 is tobefilled with a suitable liquid as'water, oil or any other liquid whichcan be introduced into the chamber. This liquid serves as a support forthe tank bottom 9, and may be maintained at a pressure approximatelyequal to the pressure induced by the head of liquid within the tank.

The inlet pipe l5 serves to introduce the liquid and is controlled by avalve 5. A standpipe I8 has been connected to the inlet pipe [5 betweenthe valve l6 and the tank. This standpipe rises to an elevation atpreferably equal to the height of the entire tank 2|. In this manner ifthe tank were filled with liquid of the same specific gravity as thechamber 12, then the pressure would be exactly balanced, when the headsin the standpipe and in the tank are equal. If the tank is filled with aliquid having a less specific gravity than the liquid I2, then the headin the stand pipe must be proportionately less than the head of liquidin tank 3!. On the other hand in some instances there may be a vaporpressure in the top of the tank, but the curved bottom tank head isdesigned to resist this pressure. When a tank or container has a fiatbottom and is subjected to an internal vapor pressure the pressure onthe top of the tank tends to lift the tank and tends to curve the bottomso that when a tank is designed to withstand an internal Vapor pressureas well as a fluid load the base is constructed of a regular or curvedshape such as spherical, conical, or ellipsoidal configuration so thatthere will be little or no tendency for it to buckle under pressure.

In order to exhaust any air or vapor which may occur in the chamber l2 avent pipe has been provided which is controlled by a valve 25 andterminates in an upstanding pipe 2! inside of the chamber l2 closelyadjacent the point ID at the top of the chamber l2.

The tank body may be of any desired configuration and extends above thearea l0 and carries the top portion 3| of the tank. A pres sure reliefvalve 32 and vacuum relief valve 36 may be provided on the top of thetank. The inlet and outlet pipes. for the liquid within the tank are notshown as they are conventional and form no part of the invention.

If desired a pressure gauge 40 may be fixed to the tank and the pressureresponsive element 4| thereof disposed in the chamber [2 closelyadjacent to the tank bottom so as to indicate the pressure on the liquidin the chamber l2. A similar gauge 42 may have its pressure responsiveelement 43 inside of the tank bottom 9 to indicate the pressure therein,whereas a third gauge 44 has its pressure responsive element 45 insideof the top of the tank above the liquid level to indicate the vaporpressure.

It seems obvious that the pressure gauge 40 should be maintained at sucha reading so that the pressure in the chamber I2 will alwayssubstantially equal the difierence between the readings on the gauges 42and 44 because this difi'erence wil1 indicate the pressure of the liquid35 and this is the pressure which should be balanced by the liquid inthe chamber l2.

As an instance, if the liquid 35 stands at 30 feet above the bottom ofthe tank and its density is 43 pounds per cubic foot, the liquidpressure at the bottom of the tank is approximately 9 pounds per squareinch. If the gas or vapor pressure above the liquid 35 is 15 pounds persquare inch, then the reading on pressure gage 44 is 15 pounds persquare inch and the reading on pressure gage 42 is 24 pounds per squareinch. For this condition the pressure on gage 45 of the liquid incompartment l 2 should be the difference between the gage readings at 42and 44 or 9 pounds per square inch, and assuming the liquid incompartment 12 to be water with a density of 62.4 pounds per cubic foot,the height of liquid in standpipe I8 is approximately 2| feet above thebottom of the tank. Then the internal pressure on the base I ofcompartment [2 balances the external pressure on the base 1 necessary tosupport the entire structure and its contents. The pressure on the topof tank bottom 9 is the difference between the readings on gages 40 and42, or 15 pounds per square inch which is the gas or vapor pressure atthe top of the tank, and curved head 9 is proportioned to resist thispressure under all conditions of loading.

The provision of the features just described permits the construction ofthe tank bottom 9 to be relatively thin steel plate material because theliquid pressures on it are substantially balanced, and is designed toresist vapor pressure only. This results in a very. economicalconstruction due to the cost of materials and the arrangement of thebase by omitting an expensive foundation, also contributes to theeconomies of the invention.

When the tank is being emptied the outlet vent 50 will be opened so asto drain the liquid I2 out of the chamber in proportion to the reductionin liquid pressure inside of the tank as the liquid is discharged. Whenthe tank is being filledthe chamber l2 may be filled to apply pressurein proportion to the rateat which the tank is being filled.

While manually operated valves are shown and described for regulatingpressure of the fluid l2, in actual practice the same results may beattained by mechanically or electrically operated valves, actuated andcontrolled by the same pressures and pressure differentials alreadydescribed for the three indicating gauges. Or the closed compartment maybe filled, compressed, decompressed and emptied, as required, withoutthe use of valves or standpipe, by using for the purpose a pump withautomatic controls and the two way valve. All valves, pressureindicating gauges and pump may be placed at a convenient location remotefrom the immediate vicinity of thetank.

Fig. 2 shows a similar construction to that described in connection withFig. 1 except that a spherical container or tank has been shown. Thearrangement of the parts however is identical with that described inconnection with Fig. 1 except that the earth's surface may be excavatedslightly to accommodate for the roundness for the spherical bottom ofthe tank. The same reference characters have been applied to Fig. 2 ashave been used in Fig. 1.

Broadly the invention contemplates a liquid supporting base for tanks sothat the load will be distributed over the entire cross sectional areaof the tank and wherein the pressures on the tank bottom may be balancedto eiie'ct additional economy.

What is claimed is:

1. A tank comprising a closed tank body constructed to withstandinternal fluid pressure and having a curved base portion of the diameterof the tank, a base for said body, said base comprising a supportingbottom. having a depressed central portion substantially complementaryto the curved base portion of the body, said base being uniformlysupported from beneath, side walls attached to the supporting bottom andextending upwardly therefrom, the upper ends of said Walls beingsealably anchored to the curved base portion of the tank body to form anenclosed chamber within the base and beneath the tank body, and a liquidfilling said chamber whereby the tank and contents are supported by apressure exerted uniformly over the entire area of the base portion.

2. A combination tank and hydraulic supporting base therefor comprisinga tank, a concave bottom therefor, a base of the diameter of the tank,including upstanding side walls of the diameter of the tank rigidlysecured in sealing relation to said tank about the periphery of thebottom so as to enclose said bottom and form a chamber therebeneath, andmeans to maintain a fluid under pressure in said chamber so as tosupport a load approximating the load in said tank.

ERNEST W. PITTMAN.

